JPS62126879A - Starting method for motor - Google Patents

Abstract

PURPOSE:To reduce a starting current and to obtain a high starting torque by RAM-controlling a comparator and PWM-controlling an inverter. CONSTITUTION:A starting frequency signal from a starting frequency setter 1 is supplied to a voltage setter 15 and a frequency setter 16 at starting time. A converter 22 is PAM-controlling in response to the output of the setter 15. Changeover switches 34, 35 are switched to b-contact side at starting time, a DC voltage Vd, a reversely induced voltage VH of an induction machine 30, and an output of a PWMalpha-calculator 7d are supplied as voltage data Vs, and the output of a starting frequency calculator 7e is supplied as frequency data Fs to a PWM circuit 7 of an inverter 17. When the inverter frequency coincides with the starting frequency, the switches 34, 35 are switched to a-contact side, and a set changeover switch 3 is switched to a frequency setter 2 side.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application This invention relates to a method for starting an electric motor using a forward/inverse converter.

B0 Summary of the Invention This invention provides a method for starting an electric motor using a PAM-controlled forward converter and a PWM-controlled reverse converter, in which the DC voltage of the PAM-controlled forward converter is transferred to the PWM-controlled reverse converter. 4. At startup, PWM control output is used, and then from PWM waveform by PWM control, P A M l! I
Since the motor is fully started using PWM control so that the PAM waveform gradually approaches the PAM waveform at the time of 11th control, a high starting torque can be obtained and the inrush current of the motor can be suppressed.

BACKGROUND OF THE INVENTION C0 Conventional Technology A high-voltage conductive motor (IM) is normally used as a drive motor for industrial large-medium capacity pumps, prowers, etc.

In recent years, I
It has become common practice to vary the speed of M using an inverse converter (inverter).

D1 Problems to be Solved by the Invention Normally, when starting with an IMi inverter, a low frequency starting method is used to suppress rush current. However, the drive motor for Proa produces 2O when starting.
It requires a high starting torque of about 4, and the P
When low frequency starting is performed using only WMIl control, there is a problem in that high starting torque cannot be obtained.

For this reason, in the present invention, the forward converter (funverter) is controlled by PAM and the inverter is controlled to the field to reduce the starting current and obtain high starting torque.

Means for Solving the E0 Problem This invention provides a method for starting an electric motor using a PAM-controlled forward conversion device and a PWM-controlled inverse conversion device, by changing the setting value of the starting frequency setter to the frequency control section. is applied to the arithmetic processing section of the inverse conversion device and the forward conversion device through the inverter to increase the output voltage of the forward conversion device to the set value and also increase the output voltage of the inverse conversion device to the value set by the arithmetic processing section. After that, after confirming whether the 911 aircraft has started rotating due to the increase, the frequency of the inverter and its output voltage are calculated and increased by the arithmetic processing unit to the starting frequency setting value, and the inverter is increased. After confirming that the frequency matches the starting frequency setting value, starting is completed after a predetermined period of time has elapsed.

20 Effects In the method for starting the electric motor configured as described above, the starting frequency set by the starting frequency setter is set to 1.5H, for example.
z, the inverter is operated at this starting frequency, and the output voltage Va of the inverter is gradually increased by digital PWM control until the output voltage va reaches the set vZf value.
to rise. The PWM control output waveform at this time becomes closer to the PAM control output waveform than the DC voltage VdK of the forward converter. Therefore, high starting torque can be obtained. Thereafter, the Vlf value is increased to the starting frequency setting value, and when the Vlf value matches the setting value, the arithmetic processing section is operated to control the inverse conversion device with the analog PWM proportional-integral calculation value. At the same time, the starting frequency set value is switched to the frequency setter to increase the rotational speed of the motor and enter normal control.

G. Example An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, 1 is a starting frequency setter, 2 is a frequency setter that is operated after the start is completed, and the output of the side setter 1.2 is input to the lift prevention circuit 4 via a setting changeover switch 3. . The output of the vibration prevention circuit 4 is supplied to the summing amplifier circuit 6 via the first matching section 5. The first matching section 5 is supplied with the output of a frequency (hereinafter referred to as F) setting adjustment means 7a formed in an arithmetic processing section 7 consisting of a microcomputer. This F setting adjustment means 71L operates for picking up and analog switching. The output of the summing amplifier circuit 6 is supplied to a cushion circuit 8. This circuit 8 is formed with a characteristic curve such as that shown in the figure, so that the motor can be started smoothly.

The output of the cushion circuit 8 is amplified by the frequency control amplification circuit 10 via the second matching circuit 9 and then sent to the third matching circuit W51.
1 is given. This third matching section 11 outputs the deviation between the output of the effective current detection section 12 and the output of the amplifier circuit 10, and the deviation output is amplified by the current amplifier circuit 13, and the inverting amplifier circuit 1. 1 is input. The output of the inverting amplifier circuit 14 is fed back to the second matching section 9 and is input to the voltage setting amplifier circuit 15 and the frequency setting amplifier circuit 16.

These circuits 15 to 16 operate as a frequency control section. The output of the voltage setting amplifier circuit 15 is supplied to the positive end of the fourth matching section 18 via the voltage setting pattern circuit 17. A DC voltage Vd is supplied to the negative end of the rg4 matching section 18, and its deviation output is input to the PAMt pressure booster amplifier 9. The output of this PAM voltage amplification circuit 19 is passed through a phase shifter and a gate circuit 21 to PAM control a condylar conversion device n consisting of a thyristor. I is a DC reactor, Sa is an electrolytic capacitor, δ is a DC voltage detection section that detects a DC voltage Vd, and 26 is a DC current Id detection section.

n is an inverse converter made of a transistor, and this inverter converts the DC voltage given from the forward converter n into an AC voltage, which is supplied to the output transformer A. The output transformer 28 transforms the supplied voltage to a predetermined voltage, and then supplies the voltage to the IM 30 via the switch 29 . 31 is a transformer that detects the output voltage va of the inverter τ, and 32 is a current transformer that detects the output voltage va of the inverter.

The output of the voltage setting amplifier circuit 15 is supplied to the positive end of each of the fifth matching parts, and the output voltage Va is supplied to the negative end of the fifth matching part.
is supplied. The fifth matching section 33 outputs the deviation between the plus end and the minus end, and the deviation output is sent to the arithmetic processing section 7.
It is calculated by the PWM proportional integral (PI) calculating section 7b. The output of this calculation section 7b is the voltage data V, the changeover switch 34
The signal is supplied to the PWM generation circuit 7c via the PWM generating circuit 7c. Voltage data V8 changeover switch or at startup, it is switched to the contact side shown in the figure.

7d is the PWM phase control angle of the calculation processing unit 7 (φ calculation unit,
The output of the frequency setting amplifier circuit 16, the DC voltage Vd, and the reverse induced voltage vH of the IM 30 are input to the calculation section 7d, and an output current Ia is supplied as a limiter.

A is the frequency data F changeover switch and the open pick-up changeover switch, and the movable contact of the former switch is switched to the contact side shown in the figure at startup.

The switch 36 is connected to the a contact side shown in the figure. 7e is a calculation unit (starting frequency function of calculation processing mV), and this calculation unit 7
The output of the active current detecting section 12 is inputted to . The output of the starting F calculation unit 7e is supplied as frequency data F8 to the PWM generation circuit 7C via the F changeover switch and the pick-up changeover switch 36. The PWM generation circuit 7C generates a predetermined PWM control output from the vs and F8 data, and supplies the output to the inverse converter n via the base drive circuit A. 7f is a frequency measurement section, 7g is a frequency calculation section, the output of the zero cross comparator 39 is supplied to the f measurement section 7f, and the F calculation section 7g
The output of the drive regeneration comparator 37 is supplied to the AC output current! & is given as a limiter. 4
0 is a failure detection circuit, 41 is a transformer, and this transformer 4
A reverse induced voltage vH is obtained on the 102nd order side.

42 and 43 are switches; during inverter operation, switch 43 is turned off; when commercial power supply operation starts, switches 1 and 42 are turned off, and switch 43 is turned on. 44 is the transformer on the input side, 45 is the AC input current IAC
The current transformer 46 that takes out the AC input voltage VAC is a transformer that takes out the AC input voltage VAC.

Next, the operation of the above embodiment will be described (see FIG. 2).

First, during inverter operation, the switch 43 is turned off and the switches 29 and 42 are turned on. Here, an example will be described in which the IM 30 is started with a starting frequency of, for example, 1.5 Hz. Depending on the conditions under which the switches 29 and 43 are turned on and off, a start command RUN is input from a sequence circuit (not shown).

As a result, at time t1, the analog cushion circuit 8
．． F amplifier circuit 10. The cut-off of the frequency control section including the current amplification circuit 13 and the like and the PAMtl pressure amplification circuit 19 is released. Further, when the starting frequency is set by the starting frequency setter IK, the gate cutoff of the inverter nail is released.

Note that both the V data changeover switch and the F data changeover switch A of the arithmetic processing section 7 are switched to the b contact side.

That is, the output of the PWMα calculation unit 7d is supplied as the voltage data vs, and the output of the starting frequency calculation unit 7e is supplied as the frequency data F8. The setting output given from the setting device 1 is sent to the vibration prevention circuit 4. Addition amplifier circuit 6. The signal is inputted to the voltage setting amplifier circuit 15 and the frequency setting amplifier circuit 16 via the cushion circuit 8 and the like. The output of the voltage setting amplifier circuit 15 is sent to the PAM voltage amplifier circuit 1 via the voltage setting pattern circuit 17.
9, and the output of the circuit 19 performs PAM control on the forward conversion device n.

As a result, the DC voltage Vd at the output of the forward converter increases in accordance with the characteristics of the coupling circuit 8 to the value set in the starting frequency setting device 1 between time t1 and time t2.

On the other hand, the output of the frequency setting amplifier circuit 16 and the DC voltage Vds
The voltage l is input to the PWM α calculation unit 7d, where the firing gate phase α of the inverse conversion unit I is calculated and the PWM generation circuit 7
c. This PWM generation circuit 7c is supplied with the F calculation value of the starting frequency (F') calculation section 7e, for example, a frequency command of 1.5 Hz, and the output of the PWM generation circuit 7c is sent from the base drive circuit side to the inverse conversion section f127. Supplied. The inverse conversion device n is based on the output of the PWM generation circuit 7c)
The output voltage Va is supplied to the IM 30 under pwM control.

The PWM generation circuit 7 is configured so that this output voltage Va rises in a cushion time T1 to a starting V & set value (for example, V/f = 1.2) set by a loader (not shown).
The pulse width of the PWM waveform is adjusted in c. Note that the cushion time T1 can be varied by the loader.

When the output voltage Va reaches the starting Va setting value and the rise is completed at time t2, a wait time Tw1 is inserted at time t5t to confirm the rotation of the IM 30.

After the wait time Tw1 has passed and the time point t5 has arrived, the starting F calculation unit 7e and The frequency and P are calculated by the PWMα calculation unit 7d.
WM phase angle α is calculated, and 5p is calculated based on each calculation output.
The inverter output is increased via the wM generation circuit 7c for a cushion time t2.

The frequency is changed from υ time t5 to time t1 by the starting F calculation unit 7e.
1, and its frequency increases from time tq to time t
Check that it matches the starting frequency setting value at step 5. Note that both are considered to match if the starting frequency setting value is 0.
This is defined as the number of times the increased frequency has occurred within 5 Hz, for example, 5 times or more.

When the starting frequency setting value and the frequency match, the F data changeover switch 35'1 (supposed to match at time t5)
, the frequency data Pg to be supplied to the PWM generation circuit 7c is switched to the A contact side shown in the figure, and the frequency data Pg is supplied to the analog F setting amplifier circuit 1.
Start giving from 6 onwards. As a result, the frequency data F
a becomes an analog frequency setting output.

On the other hand, voltage data va4. of the PWM generation circuit 7c. Since the v data changeover switch A is switched to the a contact side shown in the figure, the output becomes the output of the PWM proportional-integral calculation section 7b which operates with the voltage command signal given by the analog system voltage setting amplifier circuit 15. In order to maintain stability after switching, a wait time TW2 is provided from time t5 to time t6t. The starting process is completed at time t6, and the setting changeover switch 3 is switched to the frequency setter 2 side.

By this switching, the rotation speed of the IM 30 is increased by the characteristics of the cushion circuit 8 up to the setting value of the frequency setter 2. After this, normal control operation follows the set value of the frequency setter.

Note that when the starting torque of a pump load or the like is small, stability is increased by increasing the starting frequency set value rather than increasing the DC voltage Vd. The characteristic curve shown by the broken line in FIG. 2 is made.

H0 Effects of the Invention As described above, according to the present invention, when an induction motor is controlled using a PAM-controlled forward conversion device and a PWM-controlled inverse conversion device, the inverter frequency is set to an ultra-low frequency at the time of starting. PWM control using a microcomputer is used to modulate the output voltage with a fixed pulse rate, so it is possible to suppress the rush current to the motor, and the PA
By using the direct current voltage of the M-controlled forward converter, PWM control is performed to gradually bring the output waveform of the 2wM control closer to the output waveform of the PAM control, so a high starting torque can be obtained. Further, according to the present invention, since a microcomputer is used for arithmetic processing of PWM control, various adjustments can be easily made.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention, and FIG. 2 is a time chart for explaining the operation of FIG. 1. 1... Starting frequency setter, 7... Arithmetic processing unit, 8.
... Cushion circuit, 15 ... Voltage setting amplifier circuit, 1
6... Frequency setting amplifier circuit, 19... PAM [pressure amplifier circuit, n... Forward conversion device, I... Inverse conversion device, I
...Induction motor (IM), 7b...PWM proportional integral calculation section, 7c...PWM generation circuit, 7d...PWM
Phase angle calculation section, 7e... Starting frequency calculation section. Procedural amendment (voluntary) 1. Display of the case 1985 Patent Application No. 266377 2, Name of the invention Method for starting an electric motor 3, Person making the amendment Relationship to the case Applicant (610) Meidensha Co., Ltd. 4, Agent Address: 104 Chuo-ku, Tokyo Akashi-cho 1-29 Liquid Manufacturing Building Statement “
"Scope of Claims", "Detailed Description of the Invention O" each column. (2) "Frequency control section" described in the third line of page 5 of the same book is corrected to "amplification section." (3) Correct “exit” i-“output” as stated in the sixth line of the same page of the same book. (4) "Frequency control unit" written in page 8, line 11 and page 13 @ line 3 of the same book is corrected to "amplification unit". (5) "Voltage gold" written on page 9, line 9 of the same book is corrected to "voltage vd". (6) "t3" written in the second line of page 16 of the same book is rT
*Corrected as J. (7) Correcting "matches r ts" to "matches at ts" described in line 10 of the same page of the same book. 0 or more (attached sheet) When starting the t@ machine using a conversion device. The set value of the starting frequency setter is applied to the arithmetic processing section of the inverse converter and the forward converter through the amplifier section, and the output voltage of the forward converter is increased to the set value, and the output frequency of the inverse converter is increased. After increasing the starting frequency to the set value using PWM control, and checking whether the motor has hit the rotational speed due to the increase, the starting frequency is reversely increased to the set value, and the frequency of the inverse converter is 9. A method for starting an electric motor, characterized in that, after confirming that the starting frequency matches a set value, starting is completed after a predetermined period of time has elapsed. ”

Claims (1)

[Claims] (1) When starting a motor using a PAM-controlled forward conversion device and a PWM-controlled inverse conversion device, the setting value of the starting frequency setter is passed through the frequency control unit to the arithmetic processing unit of the inversion device. is applied to the forward converter, and the output voltage of the forward converter is increased to the set value, and the output voltage is PWM controlled to the value set by the calculation unit while the output frequency of the inverse converter is fixed at an extremely low frequency. After confirming whether the motor has started rotating due to the increase, the frequency of the inverter and its output voltage are calculated by the arithmetic processing unit to the starting frequency setting value, and the PWM of the inverter is increased. A method for starting an electric motor, characterized in that the starting frequency is increased by control, and after confirming that the frequency of the inverse converter matches a starting frequency setting value, starting is completed after a predetermined period of time has elapsed.